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Article Contents

ABSTRACT

1.INTRODUCTION

2.MEASURING NEBULAR ABUNDANCES

3.CHEMICAL ABUNDANCES OF H II REGIONS IN OUTER DISKS
3.1.Early Work
3.2.M83: a Case Study
3.3.Other Systems
3.4.Results from Galaxy Surveys
3.5.Nitrogen Abundances

4.ADDITIONAL CONSIDERATIONS
4.1.Relation Between Metallicity and Surface Brightness Breaks
4.2.An Analogy with Low Surface Brightness Galaxies?

5.THE EVOLUTIONARY STATUS OF OUTER DISKS
5.1.Flattening the Gradients
5.2.Bringing Metals to the Outer Disks
5.2.1.Mixing
5.2.2.Enriched Infall

6.CONCLUSION

REFERENCES